Physics · Fluid Mechanics

JEE Main 2024 — 4 April, Shift 1 — Question 35

Given below are two statements :

Statement I : When speed of liquid is zero everywhere, pressure difference at any two points depends on equation P1−P2=ρg( h2−h1)\mathrm{P}_{1}-\mathrm{P}_{2}=\rho g\left(\mathrm{~h}_{2}-\mathrm{h}_{1}\right)

Statement II : In ventury tube shown, 2gh=v12−v222 \mathrm{gh}=v_{1}^{2}-v_{2}^{2}

In the light of the above statements, choose the most appropriate answer from the options given below.

Question figure
  1. Option A:

    Both Statement I and Statement II are correct.

  2. Option B:

    Statement I is incorrect but Statement II is correct.

    Correct
  3. Option C:

    Both Statement I and Statement II are incorrect.

  4. Option D:

    Statement I is correct but Statement II is incorrect.

Answer: B

Step-by-step solution

Applying Bernoulli's equation

P1+ρg h1+12ρv12=P2+ρg h2+12ρv22\mathrm{P}_{1}+\rho g \mathrm{~h}_{1}+\frac{1}{2} \rho v_{1}^{2}=\mathrm{P}_{2}+\rho g \mathrm{~h}_{2}+\frac{1}{2} \rho v_{2}^{2}

[h1&h2\left[h_{1} \& h_{2}\right. are height of point from any reference level]

Given v1=v2=0\mathrm{v}_{1}=\mathrm{v}_{2}=0 (for statement-1) ∴P1−P2=ρg( h2−h1)\therefore \mathrm{P}_{1}-\mathrm{P}_{2}=\rho g\left(\mathrm{~h}_{2}-\mathrm{h}_{1}\right)

For statement-2: P1+12ρv12=P2+12ρv22P_{1}+\frac{1}{2} \rho v_{1}^{2}=P_{2}+\frac{1}{2} \rho v_{2}^{2}

P1−P2=12ρv22−12ρv12P_{1}-P_{2}=\frac{1}{2} \rho v_{2}^{2}-\frac{1}{2} \rho v_{1}^{2}

P1−P2=ρghP_{1}-P_{2}=\rho g h

  ⟹  ρg h=12ρv22−12ρv12\implies \rho g \mathrm{~h}=\frac{1}{2} \rho v_{2}^{2}-\frac{1}{2} \rho v_{1}^{2}

2gh=v22−v122 \mathrm{gh}=\mathrm{v}_{2}^{2}-\mathrm{v}_{1}^{2}

Solution figure

Answer key and solution verified before publishing.

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Exam
JEE Main 2024
Subject
Physics
Chapter
Fluid Mechanics
Topic
Bernoulli's Equation and its Applications